X Factor: Celebrity viewers took to Twitter during Saturday's show to mock Simon Cowells faux pas.
While delivering his critique to reality star Megan, he claimed that he had not met her before she appeared on the show.
But this was untrue - and Simon appears to have completely forgotten the first time he actually met Megan.
She had tried out for his show Britain's Got Talent in 2009, and made it to the live semi finals of the competition.
One fan tweeted: "Simon to Megan: “I’ve never met you before this show”
Oh really? Because Megan was a semi finalist on Britain’s Got Talent in 2009, in which Simon judged, so clearly yes you have Simon".
Another added: "Megan was on another show of Simon’s a few years ago, wonder why he acting like it the first time they met".
Dermot also made a savage quip to Megan regarding her reality TV past.
He told her she needed redemption after her reality TV past, which saw her get into a lot of furious rows on shows including Celebrity Big Brother and Ex On The Beach.
Mortified, Megan agreed that her past behaviour had been "embarrassing".
She was keen to shake off her argumentative reality star image to become a pop star.
